I think it's besides the point whether or not an RDBMS can handle a given app's data; it almost certainly can. The real question is should people dogmatically choose an RDBMS for every single data persistence problem they need to solve.
While the article's title is obviously hyperbole, I think the dissent against choosing the RDBMS model of storing knowledge is a good one. I see the decision that system architects are faced with here as being an end-to-end argument: should the protections and optimizations provided by relational databases be enforced at such a low level or are dumb databases that delegate those features to other layers better design? There's decent evidence for the latter.
"Choosing the right tool for the job" does not equal "the old tool is dead".
It's not right or wrong. It's a trade-off, a design decision.
Just because a tool can do something, doesn't mean it should in every case.
Normalize as far as it makes sense for your app.